The purpose of this study was to improve the reliability and validity of skeletal age assessment using an open and compact pediatric hand magnetic resonance (MR) imaging scanner. We used such a scanner with 0.3-tesla permanent magnet to image the left hands of 88 healthy children (aged 3.4 to 15.7 years, mean 8.8 years), and 3 raters (2 orthopedic specialists and a radiologist) assessed skeletal age using those images. We measured the strength of agreement in ratings by values of weighted Cohen's κ and the proportion of cases excluded from rating because of motion artifact and inappropriate positioning. We compared the current results with those of a previous study in which 93 healthy children (aged 4.1 to 16.4 years, mean 9.7 years) were examined with an adult hand scanner. The κ values between raters exceeded 0.80, which indicates almost perfect agreement, and most were higher than those of the previous study. The proportion of cases excluded from rating because of motion artifact or inappropriate positioning was also reduced. The results indicate that use of the compact pediatric hand scanner improved the reliability and validity of skeletal age assessments.